The benefits of BAA’s integrated team approach were demonstrated in the approach to risk mitigation adopted during the foundations and tunnelling works. These had poten-tial to influence and destabilise existing tunnels belonging to London Underground and the Heathrow Express, as well as the airport taxiways and aircraft stands.

BAA, Mott MacDonald, civils contractor Laing O’Rourke, tunnelling contractor Morgan Vinci, principal subcontractors and suppliers, London Underground and Heathrow Express each contributed their own perspective, knowledge and understanding to draw up a comprehensive risk profile – an integrated menu of risks. The team also developed a thorough understanding of the full ramifications of any risk occurring. Team members took ownership of individual risks and, in advance of construction, committed to courses of action to resolve those risks.

On any construction project there are two things that cannot be tolerated: Sudden failure, in which a structure collapses without warning; and progressive failure, in which an unstoppable series of events leads to inevitable collapse. Not all risks can be eliminated – or sometimes the cost of fully eliminating them is too great to make the project economically viable. In these instances risk management strategies can be adopted. Key to risk management is the identification of trends that can be clearly identified, monitored and treated.

For the T5 groundworks contracts a simple traffic light system was instituted. The most severe risks, capable of bringing construction to a halt, were assigned red status. Amber risks were deemed tolerable but only on condition that they would be closely monitored during construction and that there should be mitigation measures in place to halt negative trends and restore values to within an acceptable range. Risks assigned green status were acceptable subject to being governed by effective risk management. In practice, redesign and close attention to construction methods and sequences succeeded in reducing all red and amber risks to green.

Clear, effective and unfettered communication between team members played a crucial role in managing risk and ensuring that issues arising during construction were dealt with immediately, without being given the time and opportunity to develop into more serious problems with potential to impact on the project schedule, quality or safety.

During construction, monitoring of structures that were vulnerable to movement was carried out in real time. Risk status was displayed on site via a real traffic light system, which shone green for the duration of the project.